Insulating and waterproofing system for storage tanks

ABSTRACT

A SYSTEM FOR INSULATING AND WATERPROOFING A CHAMBER FOR STORING LIQUIFIED GAS AT CRYOGENIC TEMPERATURES. A FIRST LIQUID BARRIER AGAINST INGRESS OF EXTERNAL LIQUID, SUCH A WATER, IS SPACED FROM THE TOP, SIDES, AND FLOOR OF THE CHAMBER, A SECOND LIQUID BARRIER, HAVING AT LEAST A BOTTOM AND SIDES, TO PREVENT EGRESS OF THE LIQUID IS SPACED FROM THE FIRST LIQUID BARRIER AND IS IN DIRECT CONTACT WITH THE LIQUID GAS. THERMAL INSULATION COMPLETELY SURROUNDS THE CHAMBER AND FILLS THE SPACE BETWEEN THE BARRIERS FOR MAINTAINING THE LIQUID GAS AT CRYOGENIC TEMPERATURE. MATERIAL FILLS THE SPACE BETWEEN THE SIDES AND FLOOR OF THE CHAMBER AND IS WATER PERMEABLE TO PERMIT THE PASSAGE OF WATER AWAY FROM THE CHAMBER. THE FILLER MATERIAL ALSO TRANSMITS THE HYDROSTATIC PRESSURE FROM THE LIQUID GAS TO THE SIDES OF THE CHAMBER FOR BEARING SUPPORT.

Jan; 26 5 1971 IBAEEAKIN 3,557,558

' INSULATING AND WATERPROOFING SYSTEM FOR STORAGE TANKS 2 Sheets-Sheet 1 Filed Jan. 27, 1969 lizflnlor sx .Bertram If Eazn (/Ohn L. (ran/7726?; (fr.

B. E. EAKIN Jan. 26, 1971 I INSULATING AND WATERPROOF'ING SYSTEM FOR STORAGE TANKS 2 Sheets-Sheet 2 Filed Jan.

C M Z 7 Patented Jan. 26, 1971 US. Cl. 61.5 13 Claims ABSTRACT OF THE DISCLOSURE A system for insulating and waterproofing a chamber for storing liquified gas at cryogenic temperatures. A first liquid barrier against ingress of external liquid, such as water, is spaced from the top, sides, and floor of the chamber. A second liquid barrier, having at least a bottom and sides, to prevent egress of the liquid is spaced from the first liquid barrier and is in direct contact with the liquid gas. Thermal insulation completely surrounds the chamber and fills the space between the barriers for maintaining the liquid gas at cryogenic temperature. Material fills the space between the sides and fioor of the chamber and is water permeable to permit the passage of water awayfrom the chamber. The filler material also transmits the hydrostatic pressure from the liquid gas to the sides ofthe chamber for bearing support.

REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part application of our copending application Ser. No. 702,471, filed Feb. 1, 1968 now abandoned.

BACKGROUND OF THE INVENTION Field of the invention and description of the prior art This invention relates to an improved system for insulating and substantially waterproofing a chamber, such as an underground storage cavern, used for storing liquified gas, such as natural gas, at substantially atmospheric pressures and at cryogenic temperatures.

In US. patent application Ser. No. 526,983, filed Feb. 14, 1966, now US. Pat. No. 3,418,812 there is disclosed an insulation system for a cavern used for the storage of liquified gases at cryogenic temperatures. Although theinsulation system described in the prior application is satisfactory in underground caverns which are surrounded by substantially dry areas, it has been found that where the caverns are surrounded by relatively wet rock and ground or where the water table is relatively high, the waterproofing of the cavern from external water is inadequate. In the prior application, it is disclosed that a water and moisture sealant is sprayed onto the internal surface of the rock cavern after excavating, cleaning, and drying. In practice, in caverns constructed in particularly wet areas, it has been found that moisture or water seeps through the sprayed sealant and not only comes into contact with the low temperature insulation to adversely affect the insulating properties of the insulation, generally a foamed plastic, but the water works its way up through the insulation to an internal liquid barrier; the low temperature in the cavern freezes the water outside the barrier. The ice, thus formed, will ultimately break the internal liquid barrier. Such a condition obviously cannot be tolerated because such breakage of this internal barrier permits leakage of the stored liquid gas. It is to be understood that the disadvantages of the insulation system of the prior application exist only where external water is excessive and the described insulation system is quite satisfactory for most applications.

SUMMARY OF THE INVENTION It is therefore. an important object of the invention to provide an improved system for insulating and substantially waterproofing a chamber for the storage of liquid gas, such as natural gas, at cryogenic temperatures and at substantially atmospheric pressures.

It is also an object of this invention to provide an improved system for insulating and substantially waterproofing a chamber for the storage of liquified gases at cryogenic temperatures wherein the improved system is particularly effective in areas where there is excessive amount of external water surrounding the underground cavern.

It is a further object of this invention to provide an improved insulating and waterproofing system for chambers used for storing liquified natural gas wherein liquid barriers are provided on opposite sides of the thermal insulating medium surrounding the cavern so that no external water may enter the cavern and so that no liquified gas may exit the cavern.

It is another object of this invention to provide an improved insulating and waterproofing system for chambers for the storage of liquified gas at cryogenic temperatures wherein the system is particularly characterized by its simplicity and economy of construction.

Further purposes and objects of this invention will appear as the specification proceeds.

In its main aspect, the present invention accomplishes the foregoing objects by providing an insulating and waterproofing system for a chamber for storing liquified gas at cryogenic temperatures by providing a first liquid barrier which is spaced from the walls or sides defining the cham- 5 her, a second liquid barrier spaced from the first liquid barrier and in direct contact with the liquid gas, insulation in the space between the barriers so as to maintain the liquid gas at cryogenic temperatures, and filler material which substantially fills the space between the walls or sides of the cavern and the first liquid barrier, the filler material being permeable to water so that water may pass downwardly along the walls or sides of the chamber and the filler material also transmitting the hydrostatic pressure of the stored liquid to the load bearing walls or sides of the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, various embodiments of the present invention are shown, wherein:

FIG. 1 is a schematic representation of one embodiment of the waterproofing and insulation system of the present invention, the chamber shown being completely below the ground;

FIG. 2 is a schematic representation of another embodiment of our invention wherein the storage chamber has its roof extending above the ground; and

FIG. 3 is a schematic representation of still another embodiment of our invention wherein the storage chamber has its roof and at least a portion of its sides extending above the ground.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the embodiment of FIG. 1, an underground cavern, generally 10, is excavated underground in a suitable manner, preferably by use of the method disclosed in copending US. patent application, Ser. No. 527,158, filed Feb. 14, 1966, now US. Pat. No. 3,407,606. The cavern 10 is surrounded preferably by rock, although portions of the cavern 10 may be surrounded by soil. The cavern has a top 12, sides 14, and a bottom or floor 16.

After forming the underground cavern 10, crushed stone, generally 22, or other water permeable material is laid along the bottom 16 of the cavern 10. Preferably, a water and vapor barrier, generally 24, is laid along the top surface of the crushed stone 22. Advantageously, the vapor barrier 24 comprises polyethylene sheeting. Above the vapor barrier 24, a concrete slab, generally 26, is laid. The concrete slab 26 is impermeable to the passage of water. The concrete slab 26 and the crushed stone 22 transmit the load from the liquid gas contained within the cavern to the load bearing rock floor 16 of the cavern 10. Thus, the crushed stone and concrete slab 26 combine to provide water permeability below the liquid stored in the cavern 10 while at the same time provide transmission of the load from the liquid gas to the rock floor 16 for vertical load bearing support.

After the concrete slab 26 is laid in the cavern 10, a first liquid or water barrier 18 is rigdly secured in a suitable manner to the top 12, sides 14, and a bottom 16 of the cavern 10. Advantageously, the water barrier 18 comprises formed steel sheets suitable for the construction and sealing method employed. The barrier is not limited to sheet metal; it can be fabricated of any material which can be properly formed, joined and sealed. Securement may be accomplished by driving metal studs into the rock surrounding the cavern 10. The studs 20 in turn are secured, as by welding, in spaced positions to the outer planar surface of the metal water barrier 18. The water barrier 18 is normally spaced from the irregular rock sides, bottom, and top 12 of the cavern 10. The metal sheets 18 used for forming the water barrier 18 generally do not conform to the irregular surface of the rock defining the cavern 10 so that voids of varying degrees are naturally formed between the water barrier 18 and the surrounding rock.

After the water or liquid barrier 18 is mounted to the bottom 16 and the sides 14 of the cavern 10, but before the upper section of the barrier 18 is secured to the top 12, the space defined between the sides of the water barrier 18 and the sides 14 of the rock cavern 10 is filled with a water permeable material 28. Preferably, the material is water permeable concrete, such as popcorn concrete or no fines concrete. This concrete material or rigid mass 28 fills the voids between the rock cavern sides 14 and the metal sides of the water barrier 18. The filler material 28 provides a threefold function. First, the voids are filled. The second function is that the material passes 'water downwardly along the sides of the cavern 10 so as to bypass the inside of the cavern 10 and thereby assist in preventing ingress of external water to the inside of the cavern. The third function of the filler material 28 is to provide transmission of the load from the hydrostatic pressure exerted by the liquid gas contained within the cavern 10 to the load bearing sides 14 of the cavern 10. The insulation 30 itself transmits the load from stored liquid to the filler material 28, which in turn passes the load on to the rock sides 14. It is important the filler 28 be water permeable. Although the filler 28 may be load bearing, it is not the water impermeable, load bearing concrete of the type disclosed in US. Pat. No. 3,196,622.

The space between the rock top 12 of the cavern 10 and the water barrier 18, as shown in the drawing, does not contain the filler material 28. No filler material 28 is required in this space because it is not necessary to transfer the bearing sup ort for the liquid gas above the liquid level in the cavern 10.

Insulating material, generally 30, is positioned in contact with the water barrier 18 in order to provide thermal insulation for the liquid gas contained within the cavern 10. The insulation 30 is preferably foamed plastic insulation, such as foamed polyurethane, formed in blocks approximately 2 feet square by 2 to 4 inches thick. The insulation 30 preferably is to provide approximately a 100 temperature difference between the surface closest to the liquid gas and its opposite surface. The foamed insulation blocks 30 are positioned on the inner surface of the water barrier 18 by the use of suitable low temperature mastics or adhesives, or by structural securing members (not shown). The spaces between the blocks are desirably taped together. A preferred procedure for positioning the block insulation is disclosed in US. patent application Ser. No. 526,983, now US. Pat. No. 3,418,812.

After the insulating blocks 30 are in place and surround the cavern 10, an inside liquid barrier 32 is secured to the surface of the insulation blocks 30. Since the liquid barrier 32 is in contact with the cold liquid gas, it must be made of a sheet material which is non-reactive with the liquid gas, such as natural gas, and it is to be unaffected by cryogenic temperatures (258 F. for natural gas). The barrier 32 prevents the egress of liquid gas from the cavern 10. Desir-ably, the liquid barrier 32 is a plasticmetal laminate, preferably a Mylar-aluminum-Mylar- Dacron laminate. It is not necessary for the liquid barrier 32 to cover the entire inner surface of the insulating blocks 30, as the barrier needs only to contain the liquid gas. For example, a liner of metal or of a laminate having sides and a bottom, but no top, may be used.

In order to avoid the presence of ground water around the exterior of the cavern 10, a sump pump 34 is positioned at or below the level of the rock bottom or floor 16 of the cavern 10. The pump 34 is enclosed within a water impermeable tile chamber 36, which is surrounded by water permeable crushed stone 38. The crushed stone 38 communicates with the crushed stone 22 above the rock floor 16 and below the concrete slab 26, and it also communicates with the water permeable concrete 28 surrounding the sides of the cavern 10. Water passes downwardly through the water permeable filler 28 and also passes along the space between the concrete slab 26 and the rock floor 16, which is preferably slanted to flow water to the sump chamber 36, through the crushed stone 22, and passes upwardly into the sump chamber 36 through the crushed stone 38 where the sump pump 34, operated by an above ground motor 42 of the type which can be removed and replaced above the ground, draws 'water upwardly through the pipe 44 and passes it through an outlet 46 at the upper end of the pipe 44. The water passing through the outlet 46 is directed to any suitable place away from the lower portion of the cavern 10.

The insulating and waterproofing system shown in FIG. 1 and described above may be used in various type of tanks for storing gas. For example, the system may be used in connection with tanks located below the ground, except for the roof, or tanks having the roof and a portion of the sides above ground.

In FIG. 2 there is shown a tank 48 located below the ground G, but wherein the roof 50 is at about ground level. The roof 50, rather than being a natural underground formation, constitutes a concrete dome enclosing the top of the tank 48. The tank 48 is formed by first constructing a hole in the ground and then the bottom and sides are formed in precisely the same manner as in the cavern 10 of FIG. 1. The dilference lies in the construction of the roof 50 supported by footings or a foundation 54 around the periphery of the sides of the tank 48, which foundation provides support for the domed roof. The water barrier 18 is held to the roof 50 by studs 20 in a manner similar to that of the embodiment of FIG. 1.

In the embodiment of FIG. 3, the tank 56 includes a roof 58 and concrete side walls 60. The embodiment of 'FIG. 3 is different from the embodiment of FIG. 2 in that not only the roof 58, but also at least a portion of the side walls 60 extend a substantial distance above the ground level G. Again, the internal structure of the tank 56 is substantially the same as the embodiments of FIGS. 1 and 2.

In the foregoing description, it is seen that we have provided a waterproof storage chamber of various designs which provides thermal insulation for the liquid gas, such as natural gas, contained within the chamber. The thermal insulation is located between an outer 'water barrier 18 and a liquid gas barrier 32. Water permeable concrete 28 transfers the load support for the hydrostatic pressure of the liquid gas to the sides of the chamber and also provides a path for the passage of water around the chamber. A concrete slab and crushed stone transfer support for the weight of the liquid in the storage chamber to the floor of the chamber and provide water permeability so that the water passes under the liquid gas stored in the chamber. Water exterior of the chamber communicates with a sump pump and the excess water is pumped away from the lower portion of the chamber. The described system thus avoids water problems found with cryogenic storage chambers located in relatively wet ground.

While in the foregoing, there has been provideda detailed description of particular embodiments of the present invention, it is to be understood that all equivalents obvious to those having skill in the art are to be included within the scope of the invention as claimed.

What we claim and desire to secure by Letters Patent is:

1. A system for insulating and substantially waterproofing a storage chamber having a floor, sides, and a top, wherein said chamber is used for the storage of liquified gas at cryogenic temperature, said system comprising a first liquid barrier spaced from said floor, sides, and top, a second liquid barrier spaced from said first liquid barrier for containment of said liquified gas, thermal insulation substantially filling the space between said barriers for maintaining said liquified gas at said cryogenic temperature, and water permeable concrete substantially filling the space between the sides of said chamber and said first liquid barrier said water permeable concrete passing liquid downwardly between said sides and said first liquid barrier towards the floor of said chamber, said water permeable concrete also transferring lateral load bearing support for the hydrostatic pressure of the liquified gas contained within said chamber to the sides of said chamber.

2. The system of claim 1 wherein the floor of said cavern includes means for passing liquid from between the floor of said cavern and said first liquid barrier while also transferring vertical load bearing support for the liquid gas contained within said cavern to the floor of said cavern.

3. The system of claim 2 wherein pump means communicate with the floor and sides of said cavern for pumping the liquid passing between said first barrier and sides and passing above the floor of said cavern to a position away from said floor.

4. The system of claim 1 wherein said first water barrier comprises sheet metal, and said second water barrier comprises a metallic-plastic liner impervious to cryogenic temperatures and said liquid gas.

5. The system of claim 1 wherein said insulation means comprises foamed plastic insulation.

6. The system of claim 5 wherein said foamed plastic insulation comprises blocks about 2 feet square and about 2-4 inches thick.

7. The system of claim 1 wherein the floor of said chamber includes means for passing liquid from between the floor of said chamber and said first liquid barrier while also transferring vertical load bearing support for the liquid gas contained within said chamber to the floor of said chamber, and pump means communicate with the fioor and sides of said chamber for pumping the liquid passing between said first barrier and sides and passing above the floor of said chamber to a position away from said floor.

8. The system of claim 1 wherein said insulation means comprises foamed plastic insulation.

9. The system of claim 1 wherein said top of said chamber extends above ground level.

10. The system of claim 1 wherein said top and at least a portion of said sides extend above ground level.

11. The system of claim 1 wherein said chamber is an underground cavern.

12. The system of claim 11 wherein said cavern is substantially surrounded by rock, the space between the rock top of said cavern and said first liquid barrier is void, the space between the rock sides of said cavern and said first liquid barrier is filled with said water permeable concrete, and the space between the rock floor of said cavern and said first liquid barrier is partially filled with water permeable gravel.

13. The system of claim 12 wherein a sump pump communicates with said floor and sides for pumping liquid passing around said cavern to a position away from said floor.

References Cited UNITED STATES PATENTS 2,413,243 12/1946 Neff 6l.SX 2,984,050 5/1961 Crooks 52169X 3,017,722 1/1962 Smith 52169 3,020,618 2/1962 Eward 52l69 3,151,416 10/1964 Eakin et al. 61-.5X 3,196,622 7/1965 Smith et al. 61.5X 3,326,011 6/1967 Sparling 61.5X 3,418,812 12/1968 Khan et a1. 61.5

PETER M. CAUN, Primary Examiner 

